Cutting into Ductwork to add addition register vent


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Old 07-11-12, 02:04 PM
L
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Cutting into Ductwork to add addition register vent

I've read a lot about cutting into existing ductwork to add an additional register in a specific room and even added one in my son's bedroom. His room used to be noticably colder in winter and warmer in summer and they said it was because it was above the garage. He has acute asthma and neither of these conditions is good. All 3 bedrooms are above the garage yet his room had the issue. I just tested the temp in his room and it is now 3 degrees colder than the main living area...so I must have done something right :-) Now I have to close one register off in winter and summer as it gets too hot or too cold in his room!

Now I would like to add an additional register to the living room/dining room/kitchen area...which is relatively 'open' and very difficult to maintain even a 78 or 77 degree temp in the summer AC without the unit running all day and late into the eve, even using the central air and circulating fans. They tell me the furnace and AC are suffice. I could give details on them if necessary but I don't think their rating is an issue. I've drawn a sketch of the area in question and attached it as an image, along with notes of specs.

I would like to add the register between the living room and dining room area however as you can see in the drawing...the main truck of the ductwork ( in the finished ceiling in the gameroom below) is in an odd area relative to the dining room/living room, which would put the vent smack in the middle 2/3rds of the dining area.

So I am left with cutting into the 8" duct that leads off of the trunk, to the living room register which is in an over hang under the 8' window. The register in the gameroom is cut directly into the ductwork, which blows down into that room, which is 25 x 15. Even with ALL of the lower level registered closed and sealed - the living area still has its issues and the lower level is very cool.

Can I afford to cut this new register into the 8" ductwork in the living room and not mess up the 'proverbial balance and static pressure' I keep reading about. I know I can do it physically, but I am not sure about this other stuff and I sure don't want to be cutting holes in my Pergo floors just for fun. I have enough other stuff to fix around here as it is :-) Sorry for being so lengthy.

Thanks much,
Liv
 
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Old 07-11-12, 05:50 PM
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All branch lines need to come off the main duct. You will steal air from the other duct if you do cut into it
 
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Old 07-12-12, 10:15 AM
L
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Re: Cutting into ductwork to add additional register vent

Thanks for replying, but I am confused? When I added the additional vent in my son's room, I cut into the same 8" round that already supplied his room, but I cut into it about 6" away from the main duct. The vent that was originally in his room comes up under his window, which is in the overhang like the living room one. Both of those vents in his room now pour out the air.

Would it be ok to cut into the 8" round duct very close to where it comes off of the main in the living room/dining room area, so that the air supply would be more centrally located in this huge area as opposed to just on the parameters? I can't cut into the main and add any ductwork for a new vent as the ceiling is finished drywall and the main duct is less than 3 feet from the center of my dining room...which would look ridiculous.

Here are some pics of the main and the ducts if it matters any. If I would have had my brains on, I would have done something 2 years ago when I gutted the gameroom L
 
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